Dielectric relaxation studies on nanocomposites of rubber with nanofibrillated cellulose

In this work we present a study in nanocomposite rubber films with different amounts of nanofibrillated cellulose (NFC), extracted from the rachis of date palm tree. The nanocomposite films were investigated using impedance spectroscopy. The pure matrix presents three processes: α relaxation corresponding to the glass transition, a water polarization relaxation and an ionic conduction phenomenon. The incorporation of NFCs increases the dielectric losses and is responsible for other relaxation processes, directly related to the filler. A first phenomenon is associated to the presence of residual lignin and extractive substances at the surface of the filler, and a second one is due to an interfacial polarization. A dual effect of adding nanofillers in the Tg behavior was observed. The effect of water is becoming increasingly important with NFC content. The dielectric relaxation strength increases as a function of the filler concentration up to a threshold value.